For patients and other persons restricted to bed for extended periods of time, there arises the possibility of decubitus ulcers forming. Decubitus ulcers (also referred to as bed sores, pressure sores or pressure ulcers) are formed due to an interruption of blood flow in the capillaries below skin tissue due to pressure against the skin.
The highest risk areas for such ulcers to form are those areas where there exists a bony prominence which tends to shut down capillaries sandwiched between the bony prominence and the underlying support surface. When considering the redistribution of body weight and the formation of decubitus ulcers, the trochanter (hip) and the heels are the body sites of greatest concern since these two areas are most frequently involved in decubitus ulcer formations.
Blood flows through the capillaries at approximately 32 millimeters of mercury pressure (mm Hg). This level can be somewhat lower for elderly individuals or individuals with poor health or nutritional deficiencies. Thus, for the most part, once an external pressure exceeds 32 mm Hg, capillary occlusion occurs and the capillaries no longer supply oxygen and nutrition to the skin. Therefore, tissue trauma sets in with the resultant tissue decay and ulcer formation. Movement of the individual into different positions helps in restoring blood circulation into the effected areas. Such movement is, however, not always possible or, in some instances, neglected.
Moreover, even for shorter rest periods and healthy individuals a mattress which does not relieve or reduce the pressure exerted on the user is not likely to be considered to be comfortable. On the other hand, a mattress which does not provide sufficient firmness or support is also likely to be considered uncomfortable.
Various devices are relied upon by medical personnel and the like in attempting to avoid the problem of decubitus ulcers in bedridden individuals and provide greater user comfort. For instance, air mattress overlays, air mattresses (static and dynamic), water mattress overlays, water mattresses, gel-like overlays, specialty care beds, foam overlays and various types of other mattresses have been introduced in an attempt to avoid the above noted problems with decubitus ulcers and general user discomfort.
The prior art foam overlays in combination with a mattress and the prior art specialty mattresses, suffer from many drawbacks including:
(1) insufficient pressure reduction, especially in the hip and heel area; PA0 (2) poor body/foam conformance which can lead to poor weight distribution and the development of high pressure points; PA0 (3) discomfort due to rigid foam or easily "bottomed out" pads; PA0 (4) the placement of the person too high above the underlying mattress so as to decrease user safety and limit user mobility; PA0 (5) high heat retention within the surface of the foam overlay; PA0 (6) difficulty in the positioning of sheet and bed cover material; and PA0 (7) the possibility of having the overlay shift out of place with respect to the underlying mattress.
Furthermore, mattress overlays can be economically burdensome as the pads often cost an additional $150 to $200 above and beyond the cost of the underlying mattress. Thus, a hospital or the like which is required to replace a large number of mattresses (e.g. 5,000) would require a large expenditure (e.g. $750,000 at $200 per overlay). Also the mattress overlays are likely to require replacement before a mattress would require replacement. Thus, a plurality of replacement mattress overlays would likely be required during the life of the underlying mattress.